A pilot-controlled valve is discussed in DE 101 20 322 C1, and relates to a pressure-regulating valve of a compressed air braking system of a motor vehicle, for the purpose of regulating a brake pressure corresponding to a braking pressure setpoint value. The regulating valve has a control piston that is accommodated within a valve housing, which is able to be operated linearly via a control chamber. Opposite the control chamber, the control piston borders on a working chamber. From the working chamber, a coaxial hollow pin is developed on the control piston which is used for the operation of a valve seat system. The valve seat system includes a double seat valve, a valve member actuated by the control piston being flexibly prestressed by spring arrangement against an outer valve seat.
By contrast, the hollow pin connected to the control piston forms an inner valve seat, which is stressed by the pressure in the control chamber. The two valve seats interact with a pot-like sealing sleeve, whose sealing surface comes into contact at both valve seats in a closed switching position of the controlling valve. The sealing sleeve is made up of an elastomer having a reinforcement lining that is vulcanized in. However, after some time, such an elastomeric seal demonstrates subsiding phenomena, so that the sealing effect decreases. Furthermore, such an elastomeric seal is sensitive to pressure media that are contaminated by particles. This disadvantage is of greater consequence if, as is the case here, the valve has to cope with large flow volumes, and the sealing sleeve is situated directly in the flow region of the pressure medium, because then the exposure to particles of the sealing sleeve gives rise to particularly great erosive wear.